For the coulis: In a medium saucepan over medium-low heat, combine the raspberries, sugar, orange juice and vanilla. Cook, stirring frequently, until the raspberries are completely broken down and the sauce is syrupy, 10 minutes. Strain, a little at a time, through a fine-mesh sieve into a bowl, stirring to separate the seeds. Stir the orange zest in the strained sauce. Serve warm or set aside to cool.
Put the eggs in a large bowl and whisk vigorously until frothy. Whisk in the milk and then add the flour, vanilla and salt, and whisk until combined. Carefully remove the pan from the oven and add the butter, swirling until it is melted and coats the pan. Pour in the batter and immediately return the pan to the oven. Bake until the pancake is puffed and golden brown, 16 to 18 minutes.